Advances in brain mapping including functional magnetic resonance imaging (fMRI) have increased our understanding of functional brain organization. Particularly relevant for clinical applications, fMRI has proven a useful and valid method for mapping of individual brain function and is increasingly being adopted as a pre-surgical tool to guide neurosurgical decision-making. fMRI now carries a clinical billing code reflecting its utility in minimizing the use of more invasive brain mapping techniques such as the intracarotid amytal test (Wada test) for language lateralization and intra- operative electrocortical stimulation (ECS) for localization of critical brain regions. Traditional fMRI requires that the subject perform a behavioral task of interest and uses correlations between task timing and signal changes to demonstrate brain areas involved in the performance of that task. Recent studies have investigated functional connectivity of brain regions as a method to functionally categorize brain regions, even during resting states. The use of fMRI data acquired during rest could offer numerous advantages if it is found to be valid and reliable. Compared to task-based fMRI that requires an expert neuropsychologist to administer and score the behavioral paradigm, resting-state fMRI could be acquired by a greater range of professionals thereby making it more broadly available and cost-effective. Resting-state fMRI does not require active subject participation and may thus be particularly well-suited to patients who may have neurological deficits. Investigating functional connectivity in patients undergoing neurosurgery for brain lesions may also provide insights into the changes in brain functional organization that accompany brain injury and recovery. During the award period the research team will acquire resting-state and task-based language fMRI in 15 brain tumors patients undergoing neurosurgical evaluation and treatment. We will develop functional connectivity MRI approaches to map language function at the individual subject level. The proposed experiments will evaluate test-retest reliability and validity of resting-state fMRI for language mapping against clinical god-standard techniques in individual patients. Our hypothesis is that resting-state fMRI is reliable for language mapping, and in agreement with task-based language fMRI, Wada and ECS testing. Our goal is to improve fMRI language mapping for brain tumor surgery, and to create an easily administered test which could help standardize fMRI studies across institutions. This exploratory project will generate valuable preliminary data for larger multi-center validation of resting- state fMRI in image-guide brain tumor surgery.